I bought three sets of these valve covers. None of my cars have a TPMS system and I'm too lazy to constantly check tire pressures with a tire pressure gauge to actually avoid punctures and help with fuel economy. These baseball caps are easy to put on, easy to read, and appear to be well made. The canopy will change color from green (properly inflated or at the pressure the canopy is rated for), yellow for depressurization, and red for severe psi loss or a flat condition. Anyway, when I walk past the tires on my car, I can tell if they need airing. Cons: The tire pressure gauge doesn't tell you if a tire is over-inflated. Trolls can steal them. I found the valve stems to be steel. Let me screw the caps on so the trolls don't steal them - rubber valve stems aren't that much. Please note that the price in this listing is for four caps, not one.